The impact of inverter-like transitions on device TDDB and ring oscillators

Conventional time dependent dielectric breakdown (TDDB) test for discrete device usually ties source and drain together, i.e. V_ds = 0V. However, this condition is seldom seen in a switching logic circuit. To mimic the true behavior of a switching device in a circuit, an inverter-like AC TDDB 64-bit test array is constructed. Although this result in not only TDDB and BTI but also the combined effect of HCI, it is more realistic as well. In this paper, we investigated the impacts of HCI during transient and V_gd assisted recovery during off-state half cycle on TDDB and voltage acceleration factor (VAF). Another simple array to catch the collective behavior of a group of devices is ring oscillator (RO). RO itself is easy to be implemented and characterized for high frequency stress. TDDB data sets from discrete device array and ROs are compared to validate each other. Experiment results show a) frequency dependence exists regardless DC [1-2] or AC signal applied to drain, b) with the presence of HCI up to few hundred MHz, drain side de-trapping still lengthen TDDB lifetime. HCI domination might only occur at even higher frequency in GHz realm.